JP2017200412A - Power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply control device for protecting a loading device by suppressing overvoltage which is generated when DC power supply is applied.SOLUTION: A power supply control device comprises: a power source supply line connecting a DC power supply device and a loading device; and a capacitor connected to the power source supply line. Capacity of the capacitor is set to such capacity that a maximum excess amount to be generated during power source supply to the loading device becomes less than 25% of an input voltage with respect to inductance of the power supply control device that is determined by a configuration of the power source supply line. The power supply control device also comprises: a switch element which is interposed in the power source supply line for turning on/turning off power source supply to the power source supply line; and a power supply output control circuit for detecting that a power supply voltage from the DC power supply device becomes a predetermined voltage when the power supply voltage rises, and turning on a power source supply operation by the switch element only after the lapse of a predetermined time from the detection.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply control device, and suppresses an overvoltage generated when a DC power supply is turned on, and also prevents a load device from malfunctioning or breaking when an instantaneous drop or instantaneous power failure occurs on the power supply side, thereby protecting the load device. It is about technology.

  As a configuration for protecting the load device from the overvoltage generated on the load device side when the DC power supply is turned on, the load device is generally provided with a diode for overvoltage protection, the overvoltage generated in the load device is measured in advance and the voltage is detected. By selecting an element that can withstand the overvoltage, the overvoltage can be made durable, and when an overvoltage is detected, the load drive switch that controls the energization of the load is forced to conduct to release the overvoltage to the load side. Overvoltage protection schemes are known. However, providing such a configuration on the load device side causes an increase in the size or cost of the load device.

  On the other hand, in FIG. 1 of Patent Document 1, a voltage is applied to the protected circuit 101 through the switch 140 and the switch 140, and the switch 140 is applied after a predetermined time has elapsed since the voltage applied to the protected circuit 101 reaches a predetermined value. To prevent the overvoltage from being applied to the protected circuit. In the same document, it is described that it is possible to reliably protect the load device from an overvoltage caused by power-on by setting a time of 1 μsec to 10 μsec as the predetermined time.

  On the other hand, FIG. 2 of Patent Document 2 discloses a configuration that prevents malfunction of the load device due to instantaneous power failure. This is a timer circuit (12) that starts timing in response to the voltage becoming a low voltage below a predetermined value, and stops timing after a lapse of a predetermined time, and starts and stops at the timing start and stop timing. A power supply abnormality detection circuit (14) for outputting an alarm signal and an on / off circuit (15) for turning off the power supply module during a period in which the alarm signal is active are provided. And in this document, when a low voltage due to a momentary power failure is detected, the output of the power supply module is turned off for a predetermined time regardless of the momentary power failure time. It is described that the inconvenience that the load device malfunctions by preventing the input voltage from being restored before the operation is performed.

  Here, Patent Document 1 does not specify that the overvoltage protection circuit is provided in the load device itself, and Patent Document 2 discloses a power supply device provided separately from the load device. Therefore, it is considered that the load device is not enlarged or expensive.

JP 2008-104328 A JP 2009-303295 A

In Patent Documents 1 and 2, an on / off circuit of a switch and a power supply module is used. These documents are respectively for the purpose of protecting the load device from overvoltage and the purpose of preventing the malfunction of the load device at the momentary power failure. The disclosed configuration is disclosed. However, there are various types of DC power supply devices that are actually used, and a configuration that can be used for any DC power supply device is not considered.

  Accordingly, an object of the present invention is to provide a power supply control device that can be configured easily and can be applied to various DC power supply devices and can reliably protect a load device.

  Therefore, the present invention is a power supply control device interposed between a DC power supply device and a load device, the power supply line connecting the DC power supply device and the load device, and connected to the power supply line A capacitor, the capacitor having a capacity such that the maximum overshoot generated when power is supplied to the load device is less than 25% of the input voltage with respect to the inductance of the power control device determined by the configuration of the power supply line It is characterized by that.

  In the present invention, the switch element inserted in the power supply line to turn on / off the power supply to the load device, the power supply voltage from the DC power supply device is monitored, and when the power supply voltage rises, the predetermined voltage is It is possible to provide a power output control circuit for turning on the power supply operation by the switch element and a time measuring time setting circuit only after a predetermined time has elapsed after the detection.

  According to the present invention, by paying attention to the inductance of the power supply line that causes overvoltage generation and the resonance phenomenon caused by the capacitor mounted on the power supply control device, the transient response characteristic of the load device can be selected by appropriately selecting the capacitance of the capacitor. Is improved. Also, the power supply voltage from the DC power supply is monitored, and when the power supply voltage rises, it is detected that the predetermined voltage has been reached, and the power supply operation by the switch element is turned on only after a predetermined time has elapsed after the detection. The configuration is adopted. As a result, it is possible to suppress overvoltage generated at the time of turning on, switching and replacing the power supply without providing an overvoltage protection circuit in the load device or power supply device, and regardless of the form of the DC power supply device, and preventing destruction of the load device. It will be possible to respond to the momentary power interruption.

FIG. 1 is a block diagram showing a configuration of a power supply control device according to an embodiment of the present invention. It is the circuit diagram which modeled the structure of FIG. FIG. 3 is a diagram simulating overshoot that occurs when a capacitor capacity is not properly selected in the circuit of FIG. 2. FIG. 3 is a diagram simulating a case where a capacitor capacity is appropriately selected in the circuit of FIG. 2.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  Referring to FIG. 1, a power supply control device 3 according to an embodiment of the present invention is interposed between a direct current (DC) power supply device 1 and a load device 2. The power supply control device 3 generally includes a power supply output circuit 10, a power supply output control circuit 20, a control circuit power supply circuit 30, a voltage value detection circuit 40, and a time measuring time setting circuit 50.

  The power output circuit 10 is a switching element using a P-channel FET or an N-channel FET, an IC incorporating a P-channel FET or an N-channel FET, and an IC capable of controlling the P-channel FET or the N-channel FET. It is arranged on a power supply line between the DC power supply device 1 and the load device 2 and turns on / off the power supply to the load device 2 in accordance with a control signal from the power output control circuit 20.

  The power supply output control circuit 20 is supplied with power from the control circuit power supply circuit 30 and has a function of monitoring the voltage supplied from the voltage value detection circuit 40 and a time measuring function. A control signal for controlling the on / off operation of the circuit 10 is generated. In the present embodiment, the power output control circuit 20 detects that the predetermined voltage is reached at the time of rising of the power supply voltage, and performs the power supply operation by the power output circuit 10 only after a predetermined time has elapsed after the detection. Turn on. That is, the power supply output control circuit turns off the power supply operation by the power supply output circuit 10 when such a condition is not satisfied (when the voltage is less than a predetermined voltage or the like).

  The voltage value monitored by the power supply output control circuit 20 can be set by the voltage value detection circuit 40 using a voltage dividing circuit connected to the power supply line from the DC power supply device 1. In addition, the predetermined time that the power output control circuit 20 measures can be set by a time measuring time setting circuit 50 using a capacitor. This predetermined time is set to a time of 0.5 seconds or more in consideration of chattering when the DC power supply 1 is turned on, or when the DC power supply 1 is a battery, and a connector insertion error occurs when the battery is replaced. To do. If the predetermined time is set in this manner, the power supply voltage is sufficiently stabilized, and a step-like power supply voltage can be input to the load device 2.

  The control circuit power supply circuit 30 is a constant voltage circuit that is inserted between the DC power supply device 1 and the power supply output control circuit 20 to operate the power supply output control circuit 20, and includes a three-terminal regulator and an oscillation prevention circuit. For example, a capacitor of about 0.1 μF is used. Furthermore, a resistor of several Ω may be mounted to prevent this inrush current to the capacitor. In addition, elements such as a shunt regulator and a Zener diode may be used instead of the three-terminal regulator.

  In the present embodiment, the power supply voltage input from the DC power supply device 1 is supplied to the power supply output control circuit 20 via the control circuit power supply circuit 30. The power supply output control circuit 20 monitors the power supply voltage supplied from the voltage value detection circuit 40 and starts measuring time when the voltage reaches the predetermined voltage set by the voltage value detection circuit 40. When a predetermined time set by the time measuring time setting circuit 50 elapses, a control signal is output to the power output circuit 10, and in response thereto, the power output circuit 10 turns on the power supply to the load device 2. . In addition, when the power supply voltage input from the DC power supply device 1 decreases (including interruption) and becomes less than a predetermined voltage, the power supply output control circuit 20 turns off the power supply output of the power supply output circuit 10 to the load device 2. Thereafter, when the input of the power supply voltage from the DC power supply device 1 is recovered and becomes a predetermined voltage, a control signal is output to the power output circuit 10 after a predetermined time has elapsed from that point, and in response to this, a power output control is performed. The circuit 20 turns on the power output of the power output circuit 10 to the load device 2 again.

The configuration of the present embodiment is not limited as long as it is a DC power supply that supplies direct-current power to the load device 2, that is, the DC power supply device 1 is any of an AC / DC converter, a DC / DC converter, a battery, and the like. Even if it is the form of, it can respond.
In addition, since the power supply to the load device 2 is turned on after an appropriate predetermined time has elapsed since reaching the predetermined voltage, the load device in an unstable state of the power supply voltage generated when the power is turned on or when the power is replaced The power supply output to the load device 2 can be interrupted without turning off the power supply module (that is, the power supply output is maintained) as in Patent Document 2 even when an instantaneous power failure occurs. Thus, it is possible to prevent the load device from being broken or malfunctioning. This is an advantageous configuration when a power source such as a battery that does not have a function of turning on / off the output of the power supply module is used.

  The power supply control device load according to the present embodiment is not provided with a mechanism that responds to an overvoltage such as a switch or a diode as in Patent Document 1 in order to protect the load device. Instead, the present invention pays attention to the resonance phenomenon caused by the inductance L of the power supply line and the capacitor C mounted on the power control device, which causes overvoltage, and the overvoltage (overshoot amount) applied to the load device 2 is reduced. Such a circuit configuration is adopted. As described above, the operation of the power supply output control circuit 20 causes the power supply voltage to be input in steps to the load device via the power supply control device. At this time, since the inductance L, which is a second-order lag (vibration) element, is unique to the power supply line, an overvoltage (maximum overshoot) that particularly adversely affects the load device 2 by appropriately selecting a capacitor in the power supply control device 3. Generation) can be suppressed.

That is, in this embodiment, the rise time and settling time are shortened by increasing the resonance frequency (fr = 1 / 2π (LC) ^1/2 ) or the natural angular frequency and decreasing the damping coefficient, and the maximum The amount of overshoot is reduced to accelerate the attenuation. Specifically, since the inductance L is a specific value determined according to the configuration of the power supply line, the transient response characteristic depends only on the capacitance of the capacitor C of the power supply control device 3, and this is the minimum necessary. By setting the capacity to a limit, the resonance frequency can be increased and overvoltage can be suppressed.

  The inventor conducted a simulation based on the equivalent circuit shown in FIG. Here, in FIG. 2, the value L1 of the inductance L is a constant value based on the configuration of the power supply line, and here, 2.2 μH is assumed. Moreover, the resistance R is an equivalent resistance of the load device 2, and if it is a general load device 2, it is appropriate if the resistance value R1 is assumed to be 10Ω to 100Ω. On the other hand, the capacitor C is inserted in the power supply line from the DC power supply device 1 to the load device 2 and is a constituent element of the power supply output circuit 10, the power supply output control circuit 20, or the control circuit power supply circuit 30. Can do.

  The inventors simulated the response when the capacitance of the capacitor C was 100 μF and 0.1 μF and the power supply voltage of 15 V was applied, and the results shown in FIGS. 3 and 4 were obtained. As shown in these figures, in FIG. 3 where the capacitance is as large as C1 = 100 μF, a maximum overshoot amount as large as 7V (= 22V−15V) occurs, and the time for the vibration to decay becomes longer. On the other hand, in FIG. 4 in which the capacitance is reduced to C1 = 0.1 μF, it can be seen that the maximum overshoot is about 0.3 V and the vibration damping time is greatly improved.

  Actually, the capacitance C1 of the capacitor C can be determined as appropriate according to the value L1 of the inductance L and the withstand voltage performance of the load device 2. However, increasing the capacitance of the capacitor is a rush when starting or replacing the DC power supply device. This leads to an increase in current, leading to an increase in the component price of the power supply control device 3. For this reason, in the present invention, the capacitance of the capacitor is reduced. Thus, through various experiments and simulations, the present inventor has generally found that C1 <1 for ceramic capacitors in order to suppress the maximum overshoot to less than 25%, preferably less than 10% of the input voltage for L1 = 1 to 10 μH. It was confirmed that 0.1 μF is preferable.

  The present invention is not limited to the above-described embodiment and the modifications described in various places, and various modifications and changes can be made.

  For example, by using a variable resistor in the voltage dividing circuit used in the voltage value detection circuit 40 and / or using a variable capacitance capacitor in the time measurement time setting circuit 50, the predetermined voltage and / or time measurement can be adjusted. It may be possible. Alternatively, the clock time may be set based on the clock oscillator.

  Further, the capacitor C is also of a variable capacitance type, so that the voltage applied by the DC power supply device, the change of the configuration of the power supply line of the power supply control device, that is, the change of the inductance L, the change of the load device 2 or the equivalent. It is possible to cope with a change in resistance value and a change in the amount of overshoot to be reduced.

  Furthermore, in the above-described embodiment, the power supply control device corresponding to one load device 2 is exemplified, but the power supply control device corresponding to a plurality of load devices, that is, the power supply output control circuit 20 and the control circuit power supply circuit 30 are parallelized. It may be a thing.

DESCRIPTION OF SYMBOLS 1 Power supply device 2 Load apparatus 10 Power supply output circuit 20 Power supply output control circuit 30 Power supply circuit for control circuits 40 Voltage value detection circuit 50 Timekeeping time setting circuit

Claims (5)

A power supply control device interposed between the DC power supply device and the load device,
A power supply line connecting the DC power supply device and the load device;
A capacitor connected to the power supply line;
And the capacitor has a capacity such that the maximum overshoot generated when power is supplied to the load device is less than 25% of the input voltage with respect to the inductance of the power control device determined by the configuration of the power supply line. A power supply control device.   2. The power supply control device according to claim 1, wherein the capacitance of the capacitor is set to be less than 1 μF for a ceramic capacitor with respect to the inductance of 1 to 10 μH.   A switch element inserted in the power supply line to turn on / off the power supply to the load device and a power supply voltage from the DC power supply device are monitored, and the predetermined voltage is reached when the power supply voltage rises. 2. A power output control circuit that detects and turns on a power supply operation by the switch element only after a predetermined time has elapsed after the detection, and a time measuring time setting circuit. The power supply control device according to 2.   The power supply control device according to claim 3, wherein the predetermined voltage and / or the predetermined time can be adjusted.   The power supply control device according to any one of claims 1 to 4, wherein an AC / DC converter, a DC / DC converter, and a battery can be used as the power supply control device.